1. Field of the Invention
The invention relates to an electrical power transfer device such as a slipring or rotary joint. Sliprings are used to transfer electrical power between rotating parts of machines such as wind power plants, CT scanners or electrical generators. There a brush, mainly comprising electrically conductive material such as a metal or carbon is sliding on a rotating cylindrical track of conductive material, called the sliding track. Common materials for such tracks are steel, bronze or brass, sometimes being gold or silver-plated. At least one or a plurality of sliding tracks is held by an insulating material forming a module. Modules may have a shape of a disc or of a cylinder.
2. Description of Relevant Art
In the European patent application EP 0 662 736 A1 a slipring is disclosed which comprises of a plurality of wires of conductive material which are sliding in a V-groove of a sliding track of further conductive material. Due to the galvanic contact between the wires and the sliding track electric current can be transferred between the two parts rotating against each other.
The international patent application publication WO 2012/028992 discloses problems arising due to high heat developing under rotation of a slipring while transferring high currents. It further discloses a solution to handle high temperatures within the slipring by selecting specific materials.
The U.S. Pat. No. 4,849,586 discloses a slip ring based on a planar conductive plate, which has a heater located near such a planar conductive plate to prevent condensed water from freezing.
GB 2 461 533 A discloses a method for estimating and controlling of wear in wind turbine slip ring brushes by measuring the slip ring temperature and the wind turbine nacelle humidity.
A heated slipring module is disclosed in EP 2 696 449 A1 which prevents the sliding track from icing and moisture on the surface, which would decrease isolation. Various transmission systems.